多线程学习（三）

多线程的一些其他操作：

sleep

public class SleepingTask implements Runnable {

	private int countDown = 100;
	private static int taskCount = 0;
	private final int id = taskCount++;

	public String status() {
		return "#" + id + "(" + (countDown > 0 ? countDown : "lift off") + ")";
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		while (countDown-- > 0) {
			System.out.println(status());

			try {
				// old style
//				Thread.sleep(100);
				//JavaSE 5/6 style
				TimeUnit.MILLISECONDS.sleep(100);
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
				System.err.println("interrupted!");
			}
		}
	}

	public static void main(String[] args) {
		ExecutorService service = Executors.newCachedThreadPool();
		SleepingTask sleepingTask = new SleepingTask();
		for (int i = 0; i < 10; i++) {
			//线程不安全的
			service.execute(sleepingTask);
		}
	}
}

线程阻塞 使得任务调度器可以切换到另一个线程，进而可以驱动另一个任务。但是也的看底层系统实现

优先级

调度器倾向于让优先级更高的线程先执行，绝大数情况下线程以默认的优先级执行。

public class SimplePriority implements Runnable {
	private int priority;
	private int countDown=5;

	public SimplePriority(int priority) {
		super();
		this.priority = priority;
	}

	@Override
	public String toString() {
		return Thread.currentThread().getName() + " priority:" + priority + " countDown:" + countDown;
	}

	@Override
	public void run() {
		Thread.currentThread().setPriority(priority);
		while (true) {
			for (int i = 0; i < 1000; i++) {
				@SuppressWarnings("unused")
				double a = (Math.PI + Math.E) / i;// 耗时操作
				if (i % 100 == 0) {
					Thread.yield();
				}
			}
			System.out.println(this);
			if (--countDown == 0)
				return;
		}
	}

	public static void main(String[] args) {
		ExecutorService service = Executors.newCachedThreadPool();
		for(int i=0;i<5;i++){
			service.execute(new SimplePriority(Thread.MIN_PRIORITY));
		}
		service.execute(new SimplePriority(Thread.MAX_PRIORITY));
		service.shutdown();
	}
}

结果:

pool-1-thread-1 priority:1 countDown:5
pool-1-thread-6 priority:10 countDown:5
pool-1-thread-4 priority:1 countDown:5
pool-1-thread-5 priority:1 countDown:5
pool-1-thread-3 priority:1 countDown:5
pool-1-thread-2 priority:1 countDown:5
pool-1-thread-5 priority:1 countDown:4
pool-1-thread-4 priority:1 countDown:4
pool-1-thread-6 priority:10 countDown:4
pool-1-thread-1 priority:1 countDown:4
pool-1-thread-6 priority:10 countDown:3
pool-1-thread-1 priority:1 countDown:3
pool-1-thread-6 priority:10 countDown:2
pool-1-thread-4 priority:1 countDown:3
pool-1-thread-5 priority:1 countDown:3
pool-1-thread-6 priority:10 countDown:1
pool-1-thread-2 priority:1 countDown:4
pool-1-thread-3 priority:1 countDown:4
pool-1-thread-2 priority:1 countDown:3
pool-1-thread-5 priority:1 countDown:2
pool-1-thread-4 priority:1 countDown:2
pool-1-thread-1 priority:1 countDown:2
pool-1-thread-5 priority:1 countDown:1
pool-1-thread-1 priority:1 countDown:1
pool-1-thread-2 priority:1 countDown:2
pool-1-thread-3 priority:1 countDown:3
pool-1-thread-2 priority:1 countDown:1
pool-1-thread-3 priority:1 countDown:2
pool-1-thread-3 priority:1 countDown:1
pool-1-thread-4 priority:1 countDown:1

可以看出优先级高的话执行的频率更高